Ballistic missile



Oct. 3, 1961 P. E. JARNHOLT BALLISTIC MISSILE Filed April 3, 1956 INVENTOR. PER ERIK JARNHOLT ATTORNEYS United States Patent boiaget Bofors, Bofors, Sweden, a corporation of Sweden Filed Apr. 3, 1956, Ser. No. 575,834 Claims priority, application Sweden Apr. 12, 1955 10 Claims. (Cl. 102-56) The present invention relates to ballistic missiles, and more particularly to explosive projectiles of the kind in which a central body containing the explosive is rotatably disposed in an outer casing which in turn is fitted in the shell casing.

Projectiles of this kind are fired from a rifled barrel, and it is desired that the outer casing receives a spinning motion while the central body remains rotationally stationary relative thereto.

Various kinds of special bearings using layers or balls have been designed to support the central body within the outer casing so that the rotation imparted to the latter by the rifling is not transmitted to the central body. However, none of the bearing designs which are now known have been found satisfactory. As a result of the acceleration and deceleration which a projectile experiences when in flight a strong axial thrust is developed which increases the friction at the hearings to an extent such that the central body will more or less participate in the rotation of the casing. This is highly undesirable with projectiles of the kind here referred to, especially when the explosive in the projectile is of the hollow charge type.

Accordingly, the principal object of the present invention is to provide a novel and improved projectile of the general kind above referred to, in which the central body remains substantially rotationally stationary relative to the outer casing when the latter spins after the projectile is fired.

Another object of the invention is to provide a novel and improved projectile in which the central body is floatingly supported thereby preventing or at least impeding a transmission of the rotation of the outer casing to the central body.

Still another object of the invention is to provide a novel and improved projectile in which bearing means between the outer casing and the central body effectively absorb the axial thrust acting within the proiectile when in flight.

Other and further objects, features and advantages of the invention will be pointed out hereinafter and set forth in the appended claims forming part of the application.

In the single figure of the accompanying drawing, a preferred embodiment of the invention is shown by way of illustration and not by way of limitation.

The projectile according to the invention as exemplified in the figure, has a central or inner body and an outer casing. The inner body comprises a casing 1 which is closed at its bottom end by a closure member or plug 2 which is screwed into the lower end of casing 1 by means of external screw threads 2' engaging corresponding internal screw threads in casing 1. The upper end of easing 1 is closed by an inverted cone 3 preferably made of metal. The rim of the cone is formed with a cylindrical collar 3' which is seated on a narrow shoulder formed in the inner wall of easing 1. A screw ring 4 serves to secure the cone in position. The outer wall of the projectile is completed by a generally conical nose or cap 5 which is rounded at its tip and sprung upon casing 1 by means of an annular indentation 5 engaging a corresponding indentation in the outer casing wall. The inner or central ice body comprising the aforedescribed parts 1 through 5 is fitted in an outer casing 6 in which it is rotatable by means of two axially spaced mechanical bearing 7 and 8. These bearings may be of any suitable design and consist for instance of linings of appropriate material. Casing 6 is further slightly axially displaceable relative to the inner body. The outer casing 6 and the inner casing 1 define therebetween a narrow annular channel 9 slightly widened at its lower end and closed at both ends by bearings 7 and 8. Channel 9 communicates with the outside through one or several circumferentially spaced apertures 10.

An inner wall portion of casing 6 and an outer wall portion of easing 1 are formed to define a second annular channel 11 extending inwardly slanted from a point below bearing 7 toward the bottom of the projectile. As will be noted channel 11 has radial extensions at both ends. Circumferentially spaced bores 15 lead into the upper radial extension of channel 11 to connect the upper end of the channel with the outside. The lower extension issues in the bottom of the projectile and is defined by a depending flange 6' of easing 6 and a ring 14 screwed upon the bottom end of easing 1 so that functionally it becomes part of easing 1. The lower radial extension provides ingress into the lower end of channel 11.

Each of the radial extensions includes a jet or nozzlelike constriction. The upper constriction is formed by an annular rib 12 protruding from casing 1 into the radial channel or extension. Similarly, a constriction is formed in the lower extension or channel by an annular rib 13 rising from ring 14. As is apparent, the radial distances of the two constrictions from the rotational axis of the projectile are different one from the other.

The hollow interior of easing 1 is filled with an explosive charge 16 and the attendant detonating means, a detailed description of which is not essential for the understanding of the present invention.

To impart to casing 6 a spinning motion when the projectile is fired a driving band 17 is provided.

The projectile according to the invention as hereinbefore described, functions as follows:

Let it be assumed that the projectile has been fitted in a shell casing by means of flange 6, that the shell has been rammed and subsequently fired. Let it further be assumed that the casings 1 and 6 are in a position relative to each other in which either rib 12 or rib 13, both extending from casing 1 (rib 13 through ring 14-), abuts against the corresponding wall portion of easing 6 thereby closing the respective end of space 11, say, the upper end of the space.

The powder or drive gases generated by the firing of the shell will strike upon the transverse bottom surface of the projectile and the gas pressure will be distributed along the outer casing 6 and the rear surfaces of the inner body. The gases will penetrate into space 11 through the ingress opening at the lower end thereof building-up pressure in the space 11 and into space 9 through apertures 10. As a result, a force is developed which will displace casing 6 rearwards relative to casing 1 thereby closing the lower end of space 11 and opening the upper end. The pressure built-up in space '11 is now released and the rearward force exerted by it upon casing 6 decreases correspondingly. At the same time the force of the gas pressure surrounding casing 6 is so high that the gas now flowing into space 11 through bores 15 at the upper end of the space builds up a pressure in space 11 forcing casing 6 upwardly relative to the inner body. These alternating upward and downward displacements of casing 6 relative to the inner body continue until a state of equilibrium is reached in which the gas can flow freely into space'll through the ingress opening at its lower end and out of the space through the egress opening at its upper end. When this state is reached, axial bearings between the casings 1 and 6 are formed by two annular layers of gas in spaces 9 and 11. Any friction caused in bearings '7 and 8 by the axial thrust developed when the projectile is in flight is offset. As a result, casing 6 is in effect floating longitudinally relative to the inner body.

It is evident from the previous description that the formation of gas bearings is not limited to the provision of a space 11 having the illustrated configuration. It is only essential that the space has a shape such that the gas pressure will displace casing 6 relative to casing 1 in such a manner that one of the openings of the casing, preferably the rearward one, is closed.

While the invention has been described in detail with respect to a certain now preferred example and embodiment of the invention it will be understood by those skilled in the art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended, therefore, to cover all such changes and modifications in the appended claims.

What is claimed as new and desired to be secured by Letters Patents, is:

1. An explosive projectile comprising an elongated outer casing, and an inner body containing the explosive charge coaxially disposed in said casing rotatably and axially displaceable relative thereto, said casing and said body defining a space therebetween having an opening issuing in the bottom end of the projectile and an opening issuing in the outside wall of the casing, coacting wall portions of the casing and the inner body forming abutment surfaces closing the lower end of said space in the rearward position of the casing relative to the inner body and the upper end in the forward position of the casing relative to the inner body whereby said space constitutes a gas passageway between said casing and said inner body.

2. An explosive projectile comprising an elongated outer casing, and an inner body containing the explosive charge coaxially disposed in said casing rotatably and axially displaceable relative thereto, said casing and said body defining a space therebetween extending at a slant relative to the rotational axis of the projectile, said space having a bottom aperture issuing in the bottom end of the projectile and an upper aperture issuing in the outer side wall of the casing for causing drive gas generated when the projectile is fired and acting thereupon to penetrate into said space through said hottom aperture and to displace said casing rearwardly relative to said inner body, wall portions of said casing and said inner body forming coacting abutment surfaces closing the lower end of said space in the rearward position of said casing relative to the inner body and the upper end in the forward position of the casing relative to the inner body whereby said space in conjunction with said upper and bottom apertures constitutes a gas bearing.

3. A projectile according to claim 1, wherein said casing and said inner body define an annular channel therebetween, said channel constituting said space.

4. A projectile according to claim 1, wherein the wall of said casing includes at least one radial bore leading into said opening at the upper end of said space.

5. A projectile according to claim 1, wherein said casing and said inner body define said space in the form of an annular channel having a radial extension at each end.

6. A projectile according to claim 5, wherein said abutting surfaces include an annular rib on one of said coacting wall portions protruding into said extensions, each rib in conjunction with the adjacent wall surface forming a jet like orifice the cross-sectional area of which is controlled by the axial position of said casing and said inner body relative to each other.

7. A projectile according to claim 6, wherein the radial distances of said ribs from the rotational axis of the projectile are difierent one from the other.

8. A projectile according to claim 2, wherein said casing and said inner body each have a downwardly and inwardly conical wall portion, said wall portions defining said slanted space therebetween.

9. A projectile according to claim 1, wherein said casing has at its lower end a depending flange for mounting the projectile in a shell casing, the lower opening into said space being defined by the inner wall of said flange and the adjacent wall portion of the inner body.

10. A projectile according to claim 1 and further comprising two axially spaced mechanical bearing means between said casing and said inner body, the lower one of said bearings being situated above said gas passageway, the wall portions of the outer casing and the inner body between said two bearing means defining a second space closed at both ends by said bearing means, the respective wall portion of the casing including an opening leading into said second space.

References Cited in the file of this patent FOREIGN PATENTS 1,054,322 France Oct. 7, 1953 1,082,452 France June 16, 1954 734,998 Great Britain Aug. 10, 1955 

